Method of manufacturing a composite shaft

ABSTRACT

A composite shaft formed from a single flag of composite material having variable fiber orientation, and methods of forming said shaft, are disclosed herein. A preferred method includes preparing a sheet of prepreg material, dividing it into segments, deforming the segments, cutting a single flag and constructing a composite shaft from the single flag.

CROSS REFERENCES TO RELATED APPLICATIONS

Not Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to composite shafts constructed fromvariable angle plies, or flags, such that the fiber orientation variesalong the length of the shafts.

2. Description of the Related Art

Shafts made from non-metal materials, such as graphite composite, areroutinely used with sporting equipment such as golf clubs. Compositeshafts typically are constructed from multiple plies, or flags, ofcomposite that are rolled onto a tapered mandrel in a process known assheet wrapping. Each flag has a fixed fiber orientation relative to thelongitudinal axis. In general, the fiber orientations used are 0°, whichmeans the fibers run parallel to the shaft axis, ±45°, and 90°, whichmeans that the fibers extend in a circumferential direction around theshaft.

A flag extends over a finite length along a shaft axis from a startposition to an end position and is sized for a defined number of wrapsabout the shaft axis. As shown in FIG. 2, most flags are roughlytrapezoidal in shape. A unidirectional composite material typically iscomprised of fibers oriented along a given direction with resin matrixfiller in a thin layer, which forms a configuration known as a prepreg.A prepreg also typically has a backing material to maintain integrity ofthe ply during handling.

For sheet wrapped construction, changing ply orientation along thelength of the shaft requires that separate flags, oriented at differentangles, be placed along the shaft axis. The flags are made to overlap inthis construction to ensure structural continuity and strength. Thisoverlapping configuration is detrimental, however, because it increasesthe complexity of the sheet wrapping process, adds weight, and createsan uneven thickness distribution in the wall of the shaft.

In view of the above, there is a need for thin, lightweight, compositeshafts that are capable of resisting the stresses and strains placedupon them during use, particularly when they are used with golf clubequipment.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to the use of composite flags havingvarying fiber orientation along their length to construct shafts withlow weight and high structural integrity. One aspect of the presentinvention is a shaft comprising 0° fiber orientation at its tip end,where high bending stiffness is needed, and 30° orientation at its buttend, wherein more circumferential strength is required.

Another aspect of the present invention is a composite shaft comprisinga shaft axis, a butt end, and a tip end, wherein the composite shaft iscomposed of a single composite flag, and wherein the fiber orientationof the flag with respect to the shaft axis varies along the shaft axis.In some embodiments, the fiber orientation of the flag at the tip endmay be no less than 0° and no more than 15°, and further may beapproximately 0°. In other embodiments, the fiber orientation of theflag at the butt end may be no less than 20° and no more than 45°, andfurther may be approximately 30°. In some embodiments, the flag may beapproximately trapezoidal in shape. In further embodiments, thecomposite shaft may comprise a golf club head and a grip, wherein thegolf club head may be affixed to the tip end and the grip may be affixedto the butt end. In another embodiment, the composite flag may comprisea backing material, which may be composed of an open weave material.

Yet another aspect of the present invention is a method of manufacturinga composite shaft, the method comprising the steps of preparing a sheetof prepreg material, dividing the prepreg material into a plurality ofsegments, deforming each of the plurality of segments by a designatedoffset to create a deformed prepreg sheet, cutting a single flag fromthe deformed prepreg sheet, and constructing a shaft from the singleflag. In some embodiments, the step of deforming each of the pluralityof segments by a designated offset may be accomplished with a tablecomprising a plurality of parallel bars, wherein each of the parallelbars may be free to move laterally while at the same time staying incontact with each other. In some further embodiments, each bar may graspthe prepreg material, and the individual offset for each bar may beenforced in small increments until the desired offset profile isreached. In further embodiments, each bar may grasp the prepreg materialwith a device selected from the group consisting of a strap, a clampingbar, and an adhesive.

In some embodiments, the shaft may comprise a longitudinal shaft axis, atip end, and a butt end, the tip end may comprise fibers oriented at noless than 0° and no more than 15° with respect to the shaft axis, andthe butt end may comprise fibers oriented at no less than 20° and nomore than 45° with respect to the shaft axis. In a further embodiment,the tip end may comprise fibers oriented at approximately 0° withrespect to the shaft axis, and the butt end may comprise fibers orientedat approximately 30° with respect to the shaft axis. In someembodiments, the prepreg material may comprise a backing material, whichmay comprise an open weave construction. In some embodiments, the methodmay further comprise the step of slitting the backing materialperpendicular to the undeformed fiber, and this further step may occurprior to the step of deforming each of the plurality of segments.

Another aspect of the present invention is a method of manufacturing acomposite shaft, the method comprising the steps of preparing a sheet ofprepreg material, the prepreg material comprising a plurality of fibers,a resin material, and a backing material, dividing the prepreg materialinto a plurality of segments, deforming each of the plurality ofsegments by a designated offset to create a deformed prepreg sheet usinga table comprising a plurality of parallel bars, wherein each of theparallel bars is free to move laterally, and wherein the plurality ofparallel bars stay in contact with one another, cutting a single flagfrom the deformed prepreg sheet, and constructing a shaft from thesingle flag, wherein the shaft comprises a longitudinal shaft axis, atip end, and a butt end, wherein the tip end comprises fibers orientedat no less than 0° and no more than 15° with respect to the shaft axis,and wherein the butt end comprises fibers oriented at no less than 20°and no more than 45° with respect to the shaft axis.

Having briefly described the present invention, the above and furtherobjects, features and advantages thereof will be recognized by thoseskilled in the pertinent art from the following detailed description ofthe invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a front, perspective view of a golf club including anembodiment of the present invention.

FIG. 2 is a front, plan view of a typical composite ply layout.

FIG. 3 is a front, plan view of an idealized section of compositematerial.

FIG. 4A is a front plan view of a composite segment in an undeformedcondition.

FIG. 4B is a front plan view of a composite segment in a pure sheardeformation.

FIG. 4C is a front plan view of a composite segment in a combinedextension and bending deformation.

FIG. 5 is a flow chart showing a method of the present invention.

FIGS. 6A-6C are front plan views of prepreg sheets on an adjustmenttable having different lateral deformations.

FIG. 7A-7C are front, plan views of a trapezoidal flag cut from adeformed section of prepreg material.

FIG. 8 is a chart showing the offset distance versus position in avariable fiber angle composite of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, a shaft 10 used with a golf club typically includesa shaft axis 15, a butt end 12 to which a grip 20 is affixed, and a tipend 14, at least part of which is inserted into, and in many casespermanently bonded to, the hosel 26 of a golf club head 25 or a shaftsleeve (not shown) for use with an adjustable golf club head 25. Shafts10 used with golf club heads 25 typically have a length of 35 to 46inches, though they may be as short as 18 inches or as long as 48inches, as desired by the player. Composite shafts 10 are desirable foruse with golf club heads 25 because they are strong and lightweight, andfree up mass that can be used to incorporate advanced golf club head 25technology.

The present invention is directed to composite shafts 10 having variablecomposite fiber orientation along their lengths, a configuration that isparticularly useful for golf equipment. Composite shafts 10 typicallyare constructed from multiple plies, or flags 30, of composite that arerolled onto a tapered mandrel in a process known as sheet wrapping. Eachflag 30, an example of which is shown in FIG. 2, has a fixed fiberorientation relative to the longitudinal axis of the resulting shaft 10.The flag 30 has a length, L, a wrap direction dimension a at its tip end32, a wrap dimension b at its butt end 34, and a fiber angle θ, which isrelative to the longitudinal axis x of the flag 30.

In general, the fiber orientations used in a typical flag 30 are 0°,which means the fibers run parallel to the shaft axis, ±45°, and 90°,which means that the fibers extend in a circumferential direction aroundthe shaft 10. A flag 30 extends over a finite length along the shaftaxis 15 from a start position to an end position and is sized for adefined number of wraps about the shaft axis 15. As shown in FIG. 2,most flags 30 are roughly trapezoidal in shape. A unidirectionalcomposite material typically is comprised of fibers 35 oriented along agiven direction with resin matrix filler 37 in a thin layer, which formsa configuration known as a prepreg, an idealized section of which isshown in FIG. 3. As shown in FIG. 3, prepreg also typically includes abacking material 38 that is designed to maintain integrity of theprepreg material during handling.

In situations where minimum weight and structural integrity areimportant, such as with golf equipment, variable fiber orientation isbeneficial. Unfortunately, as illustrated in FIGS. 4A-4C, obtainingvariable fiber orientation can be difficult. As shown in FIG. 4A, asegment 40 of composite material, which makes up a flag 30, has singlefibers 35 along its upper and lower surfaces that contain the resinmatrix material 37. When in pure shear, as shown in FIG. 4B, the fibers35 rotate and are aligned with the local slope, dy/dx, but are notsubjected to extensional strain because no change in length takes place.Instead, the resin matrix material 37 deforms in shear only andexperiences no change in volume. This form of deformation requires verylittle force because the fibers 35 do not deform and there is no volumechange to the resin matrix material 37.

In order to facilitate this deformation process, the backing material 38typically used for handling composite prepreg can be slit perpendicularto the undeformed fiber 35 direction to allow shear deformation of theflag 30 to take place. Alternatively, another form of shear flexiblematerial, such as an open weave, can be used as backing material 38. Ifthe composite segment 40 is deformed in general bending and extension,which would occur if overall curvature of a composite flag 30 in thexy-plane were enforced, the segment 40 behaves as shown in FIG. 4C. Inthis case, the fibers 35 are subjected to extensional strains and theresin matrix material 37 undergoes a change in volume. Deforming acomposite material in this manner is difficult because the fibers 35 arestiff and resist longitudinal deformation. Additionally, changing thevolume of the resin matrix material 37 tends to cause the resin to flow.

According to a preferred method of the present invention, shown in flowchart form in FIG. 5, composite material is transformed into a variableangle flag 30 by gradually deforming the material in transverse shearalong its longitudinal axis x according to processes illustrated inFIGS. 6A-6C. As shown in FIG. 6A, a sheet of prepreg material 50 firstis divided into segments 55 along its longitudinal axis x 100. Eachsegment 55 corresponds to a longitudinal position, x_(i), along theprepreg material 50. Each of the segments 55 is then deformed by adesignated offset, y_(i) 110, which orients the fibers 35 of the prepregmaterial 50 at desired angles along the longitudinal axis as shown inFIG. 6B. As shown in FIGS. 6A-6C, the deformation step is accomplishedusing a table 60 with multiple parallel bars 65 that are free to movelaterally while at the same time staying in contact with each other. Inthis embodiment, the prepreg material 50 is held at each bar 65 by astrap, clamping bar, or adhesive, and the individual offset for each bar65 is enforced in small increments until the desired offset profile isreached. Because the fibers 35 of the prepreg material 50 are continuousand have some flexural stiffness, they do not deform in a piecewiselinear manner, and their resulting shape is a smooth curve as shown inFIG. 6C.

Once a piece of prepreg material 50 is deformed as shown in FIGS. 6A-6C,a trapezoidal flag 30 that will be used to create the shaft 10 is cut120 from a section of the prepreg material 50 according to the processshown in FIGS. 7A-7C. Table 1 provides an example of the parameters fora twenty five-inch long flag 30 that has been divided into twenty fiveequal width segments 55. Once the flag 30 is cut, a shaft 10 is formed130 by a process such as sheet wrapping or another process known to aperson skilled in the art.

TABLE 1 Position Delta Offset Angle (in.) (in.) (in.) Slope (deg) 0.00.000 0.000 0.000 0.0 0.5 0.000 0.000 0.000 0.0 1.0 0.000 0.000 0.0000.0 1.5 0.000 0.000 0.000 0.0 2.0 0.000 0.000 0.000 0.0 2.5 0.000 0.0000.000 0.0 3.0 0.000 0.000 0.010 0.6 3.5 0.010 0.010 0.030 1.7 4.0 0.0200.030 0.050 2.9 4.5 0.030 0.060 0.070 4.0 5.0 0.040 0.100 0.090 5.1 5.50.050 0.150 0.110 6.3 6.0 0.060 0.210 0.130 7.4 6.5 0.070 0.280 0.1508.5 7.0 0.080 0.360 0.170 9.6 7.5 0.090 0.450 0.190 10.8 8.0 0.100 0.5500.210 11.9 8.5 0.110 0.660 0.230 13.0 9.0 0.120 0.780 0.250 14.0 9.50.130 0.910 0.270 15.1 10.0 0.140 1.050 0.290 16.2 10.5 0.150 1.2000.310 17.2 11.0 0.160 1.360 0.330 18.3 11.5 0.170 1.530 0.350 19.3 12.00.180 1.710 0.365 20.1 12.5 0.185 1.895 0.375 20.6 13.0 0.190 2.0850.385 21.1 13.5 0.195 2.280 0.395 21.6 14.0 0.200 2.480 0.400 21.8 14.50.200 2.680 0.400 21.8 15.0 0.200 2.880 0.400 21.8 15.5 0.200 3.0800.400 21.8 16.0 0.200 3.280 0.400 21.8 16.5 0.200 3.480 0.400 21.8 17.00.200 3.680 0.400 21.8 17.5 0.200 3.880 0.400 21.8 18.0 0.200 4.0800.400 21.8 18.5 0.200 4.280 0.400 21.8 19.0 0.200 4.480 0.400 21.8 19.50.200 4.680 0.400 21.8 20.0 0.200 4.880 0.400 21.8 20.5 0.200 5.0800.400 21.8 21.0 0.200 5.280 0.400 21.8 21.5 0.200 5.480 0.400 21.8 22.00.200 5.680 0.400 21.8 22.5 0.200 5.880 0.400 21.8 23.0 0.200 6.0800.400 21.8 23.5 0.200 6.280 0.400 21.8 24.0 0.200 6.480 0.400 21.8 24.50.200 6.680 0.400 21.8

FIG. 8 shows the offset profile and fiber angle profile resulting fromthe method disclosed herein and illustrated in FIGS. 6A-6C and Table 1.In this example, the tip portion of the flag 30 has a fiber orientationof 0°. The fiber angle increases almost linearly in the middle portionto 22° and remains constant at that value for the remainder of the flag.

Shear deformation of the prepreg material 50 is a key feature of themethod of the present invention because it requires minimal force andkeeps the fiber 35 and resin matrix material 37 of the prepreg material50 intact. This method is most readily applicable to composite prepregmaterial 50 used in standard hand lay-up and sheet wrap processes.However, the backing material 38 on the prepreg material 50 must bemodified to permit shear deformation transverse to the longitudinal axisof the ply. This method may also be adapted to automated tape laying(ATL). In ATL, the tape laying head translates laterally perpendicularto the tape laying path without rotation of the head to produce thedesired slope.

The method disclosed herein provides a number of benefits for shaft 10performance. First, the composite fiber remains continuous along thelength of the flag 30, which provides increased strength and stiffnessthrough the elimination of cut fibers, overlap joints, and thicknessdiscontinuities. Furthermore, shaft 10 weight is reduced through theelimination of flag 30 overlap regions and fabrication is simplified,with one flag 30 replacing multiple flags 30 of different fiber angles.

In one embodiment of the present invention, the method disclosed hereinis used to form a shaft 10 a single composite flag having variable fiberorientation, an example of which is shown in FIGS. 2 and 6A-6C, so thatthe tip end 14 of the shaft 10, which requires high bending stiffness,has composite fibers with 0° orientation, and the butt end 12, whichrequires more circumferential strength, has composite fibers with 30°orientation.

From the foregoing it is believed that those skilled in the pertinentart will recognize the meritorious advancement of this invention andwill readily understand that while the present invention has beendescribed in association with a preferred embodiment thereof, and otherembodiments illustrated in the accompanying drawings, numerous changes,modifications and substitutions of equivalents may be made thereinwithout departing from the spirit and scope of this invention which isintended to be unlimited by the foregoing except as may appear in thefollowing appended claims. Therefore, the embodiments of the inventionin which an exclusive property or privilege is claimed are defined inthe following appended claims.

I claim:
 1. A method of manufacturing a composite shaft, the methodcomprising the steps of: preparing a sheet of prepreg material; dividingthe prepreg material into a plurality of segments of the prepregmaterial; deforming each of the plurality of segments of the prepregmaterial by a designated offset to create a deformed prepreg sheet usinga table comprising a plurality of parallel bars, wherein each of theparallel bars is free to move laterally, and wherein the plurality ofparallel bars stay in contact with each other, cutting a single flagfrom the deformed prepreg sheet; and constructing a shaft from thesingle flag.
 2. The method of claim 1, wherein each bar of the pluralityof bars grasps a segment of the plurality of segments of the prepregmaterial, and wherein an individual offset for each bar is enforced insmall increments until a desired offset profile is reached.
 3. Themethod of claim 2, wherein each bar grasps the segment of the pluralityof segments of the prepreg material with a device selected from thegroup consisting of a strap, a clamping bar, and an adhesive.
 4. Amethod of manufacturing a composite shaft, the method comprising thesteps of: preparing a sheet of prepreg material; dividing the prepregmaterial into a plurality of segments of the prepreg material; deformingeach of the plurality of segments of the prepreg material by adesignated offset to create a deformed prepreg sheet; cutting a singleflag from the deformed prepreg sheet; and constructing a shaft from thesingle flag, wherein the shaft comprises a longitudinal shaft axis, atip end, and a butt end, wherein the tip end comprises fibers orientedat no less than 0° and no more than 15° with respect to the shaft axis,and wherein the butt end comprises fibers oriented at no less than 20°and no more than 45° with respect to the shaft axis.
 5. The method ofclaim 4, wherein the tip end comprises fibers oriented at approximately0° with respect to the shaft axis, and wherein the butt end comprisesfibers oriented at approximately 30° with respect to the shaft axis. 6.The method of claim 1, wherein the prepreg material comprises a backingmaterial.
 7. The method of claim 6, wherein the method further comprisesthe step of slitting the backing material perpendicular to an undeformedfiber of the sheet of prepreg material or of the segments of the prepregmaterial.
 8. The method of claim 7, wherein the step of slitting thebacking material occurs prior to the step of deforming each of theplurality of segments of the prepreg material.
 9. The method of claim 6,wherein the backing material comprises an open weave construction.
 10. Amethod of manufacturing a composite shaft, the method comprising thesteps of: preparing a sheet of prepreg material, the prepreg materialcomprising a plurality of fibers, a resin material, and a backingmaterial; dividing the prepreg material into a plurality of segments;deforming each of the plurality of segments by a designated offset tocreate a deformed prepreg sheet using a table comprising a plurality ofparallel bars, wherein each of the parallel bars is free to movelaterally, and wherein the plurality of parallel bars stay in contactwith each other; cutting a single flag from the deformed prepreg sheet;and constructing a shaft from the single flag, wherein the shaftcomprises a longitudinal shaft axis, a tip end, and a butt end, whereinthe tip end comprises fibers oriented at no less than 0° and no morethan 15° with respect to the shaft axis, and wherein the butt endcomprises fibers oriented at no less than 20° and no more than 45° withrespect to the shaft axis.